The present application is related to, and claims priority from, Japanese Patent Application No. Hei. 10-37572, the contents of which are incorporated herein by reference.
1. Technical Field
The present invention relates generally to a mobile communications system including a terminal such as a portable telephone, and particularly to a mobile communications terminal and system in which a time displayed by the terminal can be corrected based on a reference time, while an intentional offset time can be established at the terminal without the need to modify the reference time itself.
2. Related Art
Recently, the proliferation of mobile communications terminals such as cellular telephones and personal handy-phone system (PHS) telephones has resulted in the demand for additional functions other than the basic functions of such terminals. A clock function may be considered as a general example of such an addition function. In particular, a clock function enables the terminal to display the present time, sound an alarm when a preset time is reached, or the like. In a mobile communications terminal including a time-generating unit, the terminal displays the time generated by the time-generating unit.
However, the time generated by the time-generating unit may deviate from a reference time because of, for example, removal and attachment of the battery supplying electrical power to the time-generating unit, or due to the limited accuracy of the time-generating unit itself. Consequently, correction based on a reference time is preferred to correct any such deviation.
Nonetheless, a user may have a habit of, for example, setting a time with an offset, such as purposely setting the time five minutes ahead. If the displayed time is corrected merely by matching the displayed time to the reference time, the user""s offset time is lost.
When a mobile communications terminal does not include a time-generating unit, it is sufficient that the reference time be displayed. The reference time requires no correction, but the reference time itself cannot be changed according to the user""s circumstances as described above. For this reason, when an externally-provided reference time is used, a user cannot perform an operation such as purposely setting the time five minutes ahead.
In this regard, it is a first object of the present invention to provide a mobile communications system and terminal that achieve the above-discussed time correction based on a reference time, as well as enable an intentional offset time to be added to the displayed time if so desired, without a time correction function based on the reference time eliminating the offset time.
It is a second object of this invention to provide a mobile communications system which can also accommodate setting of an intentional offset time when time displayed at the terminal is based on an externally-provided reference time.
A mobile communications terminal devised to achieve the foregoing first object is in wireless communication with a base station or base stations connected to a predetermined telephone-line network, thus enabling the terminal to communicate with other terminals of like function. A differential-storing portion of the terminal stores a differential between a time generated by a time generating portion and a reference time stored in a time storage portion. A time-correcting portion corrects a time generated by the time-generating portion based on a differential stored in the differential-storing portion and a reference time stored in the time-storing portion.
Thus, it is possible for the time-generating portion of the present invention to revise the time in accordance with an instruction input via a revision-instruction input portion because, for example, a user may have a habit of setting the display time with an offset. Thus, when a terminal display time is generated by the time-generating portion, or when an alarm or the like is activated based on the generated time, the terminal display revision instruction input from the revision-instruction inputting portion factors both the user""s intentional offset time and the reference time into the terminal display revision. In this regard, the present invention is devised to correct a terminal display time generated by the time-generating unit based on both the differential and the reference time.
It may be noted that the above-described reference time may be generated within the terminal, or acquired from an external source.
If the time is generated within the terminal, preferably a GPS (Global Positioning System) receiver receives signals from a GPS satellite, and a reference-time generating unit generates a reference time based on the received signal. Accordingly, this generated reference time may be stored in a reference-time storing portion.
If the time is acquired from an external source, preferably a receiver receives the reference time, and the received reference time is stored in the reference-time storing portion. When a cdmaOne system is utilized as a connection method, to communicate data for achieving synchronization between a mobile communications terminal and a base station, it is sufficient to have the reference time sent from the base station during data transmission. Further, the acquisition source may be something other than a base station. For example, a reference time is issued even in an electronic navigation system for a ship, and so a mode which performs direct reception from a base station or stations for such a communications system is also contemplated.
In view of the above, time with a desired offset can be displayed for a user""s convenience even in a terminal not having a time-generating unit. Additionally, time-related processing is not exclusively limited to time display, but may be processing for example relating to sounding an alarm or the like when a set time is reached.
Accordingly, a mobile communications system may be provided with a mobile communications terminal and a base station or stations, where the base station is provided with a GPS-receiver to receive signals from a GPS satellite, a reference-time generating portion to generate the reference time based on a signal received by the GPS-receiving unit, and a transmitting unit to transmit a reference time generated by the reference-time generating portion to the mobile communications terminal. Of course, the base station itself may further be structured to receive a reference time from an external source.
A representative device wherein a mobile communications terminal according to the present invention is embodied may be a telephone apparatus for mobile-unit use, such as a portable telephone (what is known as a cellular telephone or a sub-unit for PHS use), a car telephone, or the like. Further, the present invention can be applied in a terminal such as pager having no telephone function.